The present invention is directed to improvements in the anode geometry for solid electrolytic capacitors and solid electrolytic capacitors formed therewith. More specifically, the present invention is related to anode geometries which allow for higher capacitance per unit volume of the finished capacitor while also allowing for improvements in equivalent series resistance (ESR).
Miniaturization of electronics has been an ongoing effort for many years. As the demand for smaller circuits increases, there is an ever increasing demand for smaller electronic components. Unfortunately, this demand for smaller electronic components has not decreased the required electronic characteristics of the components.
Capacitors are particularly difficult to miniaturize since the overlap area of the anode and cathode, which are separated by a dielectric, is a critical parameter in the determination of capacitance. Furthermore, in a solid electrolytic capacitor, decreasing the anode volume decreases the capacitance which is undesirable. As the size of the anode decreases, the external dimensions decrease thereby decreasing the available facial surface area for the conductive cathode layer which decreases the available contact area between the cathode lead and cathode. Decreasing the surface area of cathode and decreasing the contact area between the cathode lead and cathode increase ESR, which is highly undesirable.
Efforts to mitigate the deficiencies have included the use of high CV/g powders and fluted anodes. It has proven difficult to achieve low ESR with high CV/g powders and this conundrum has limited the advances which can be realized with this approach. Fluted anodes allow for the formation of capacitors with low ESR, but this is at the expense of volumetric efficiency. Therefore, the artisan has been limited to lowering ESR or increasing volumetric efficiency but achieving both has been problematic.
There is an ongoing desire for a solid electrolytic capacitor which has improved volumetric efficiency without increased ESR. The present invention provides improvements in both.